1. Field of the Invention
The invention relates to a record carrier recording method for forming marks and lands on a recording surface of the record carrier by irradiating a radiation beam onto the recording surface of the record carrier, the radiation beam, for each mark to be recorded, being set to at least one constant or pulsed write power level capable of forming a mark during a mark period and, for each land between the marks, to at least one bottom power level incapable of forming a mark during a land period. The invention also relates to a corresponding record carrier recording device for carrying out such a method.
A mark is understood to be any area on the recording surface having optically detectable properties which differ from the properties in the surrounding land area. Examples of such a mark are a pit in an even surrounding area or an amorphous area in a crystalline surrounding area.
2. Description of the Related Art
A recording method according to the preamble is known from the Compact Disc Recordable (CD-R) system description (also known as the Orange-Book). A mark (in this case being a pit) is formed by irradiating a radiation beam having a write power level onto a recording surface of an optical record carrier during a mark period. The time length of the mark period depends on the length of the mark to be recorded. The length of a mark is represented by a parameter nT, where T represents the time length of one period of a reference clock in a data signal and n represents a predetermined integer number. For a CD-R system, n is in a range of from 3 to 11. For forming a land, the radiation beam is set to a bottom power level which is lower than the write power level during a land period.
The setting of the radiation beam to the bottom power level during the land period when writing a recordable optical medium (CD, DVD, etc.) involves problems. Due to the low bottom power level, the intensity reflected back from the record carrier to a detector fluctuates significantly during the writing process. When writing a mark, much more light falls on the detector as compared to reading in between the marks. This has a particular drawback for the detection of a wobble signal derived from a pre-pressed groove in a record carrier. Such a wobble signal is often used for storing addressing information, auxiliary data, such as, for example, write strategies, or data to be protected against unauthorized access, for example, encryption keys, on the record carrier.
For DVD-recordable (such as DVD+R), it can be seen that the wobble signal is most difficult to detect during writing. Because the wobble causes jitter in the HF channel of DVD+R media, it is, on the one hand, desired to have the wobble amplitude as low as possible. However, on the other hand, for a good wobble detection, it is desired to have the wobble signal-to-noise ratio (S/N ratio) as high as possible, which implies a high wobble amplitude. It is, therefore, desired to increase the wobble signal-to-noise ratio during writing without increasing the wobble amplitude.
The detection of the reflected bottom power level is required for a continuous optimization of the power of the radiation beam during the recording operation (often called Running Optimum Power Control (ROPC) or alpha control). This ROPC controls the recording powers such that the effects are always properly written, even in the case of, for example, fingerprints on the surface of a recording disc. However, at higher disc velocities, this detection of the reflected bottom power level becomes more difficult, because the bottom power level is relatively low compared to the write power level.
An additional problem appears during writing on recordable media where servo signals are generated by sampling the bottom power level. At higher write speeds, the noise/disturbance levels in a drive will increase.